The present invention is directed to heat exchangers of the type utilizing a liquid and a vapor in order to effect the transfer of heat.
When a heat exchanger is employed as a boiler or an evaporator, it is important to keep all surfaces wetted so that a maximum heat transfer effect occurs between the wetted surfaces and the liquid in order to create bubbles or boiling by the vapor action. As is well known in the field of refrigeration, when an evaporator is covered or filled with a liquid which is boiled by having heat applied to it through the heat exchanger surfaces, then the liquid itself has much higher density, usually, than the vapor which is created by boiling. Certain aspects of the foregoing are set forth in Applicant's prior U.S. Pat. Nos. 3,312,054 dated Apr. 4, 1967; 4,139,054 dated Feb. 13, 1979 and 4,159,735 dated July 3, 1979.